Mammalian epidermis is a tissue in which cells progress from a germinative cell layer through a series of specific differentiation events to a terminally differentiated state in the stratum corneum. The focus of our research is the regulation of this process of epidermal differentiation of which keratin is the major product and a component of the epithelial cytoskeleton. During the next year we shall examine the controls for expression of this product at several levels. We will continue to characterize keratin mRNA and will explore its role in the control processes. We will examine the quantitative control of epidermal protein synthesis in tissue slice, cell free and tissue culture systems. We will also explore post-translational protein modification events including phosphorylation.